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61.
Synthesis, processing, and secretion of rat immunoglobulin E made in Xenopus oocytes 总被引:1,自引:0,他引:1
Rat immunoglobulin E (IgE) synthesized in Xenopus laevis oocytes, injected with rat plasmacytoma mRNA, was analysed by specific immunoprecipitation and SDS-polyacrylamide gel electrophoresis under reducing as well as non-reducing conditions. The results indicate that the oocytes will translate and correctly process the rat IgE heavy and light chains, resulting in secretion of a correctly assembled, normal immunoglobulin molecule. The normal, extensive glycosylation of the IgE heavy chain (e-chain) is faithfully carried out by the oocytes; therefore, this posttranslational modification is apparently of an unspecific nature, and does not depend upon a mechanism specific for plasma cells. 相似文献
62.
Wet strength improvement of unbleached kraft pulp through laccase catalyzed oxidation 总被引:24,自引:0,他引:24
Previous investigations have shown that laccase catalyzed oxidation of lignin containing wood fibers can enhance the strength of medium density fiberboards. In the present work it was investigated if laccase treatment had any impact on the tensile strength of a high yield unbleached kraft pulp. Treatment with laccase alone had only a very little effect on the wet strength of the pulp, whereas addition of lignin rich extractives increased the wet strength after the enzyme treatment significantly. A mediated oxidation gave a similar improvement of the wet tensile strength although no lignin was added to the fiber suspension. Furthermore, it was found that a heat treatment combined with a mediated oxidation gave a higher improvement in wet tensile strength than could be accounted for by the individual treatments. No change in dry tensile strength from the laccase treatment was observed. It is suggested that the observed improvement in wet tensile strength is related to polymerization of lignin on fibers in the hand sheet and/or coupling of phenoxy radicals on lignin associated to adjacent fibers. For the different mediators studied, a correlation was found between oxygen consumption upon mediated oxidation and generation of wet strength in the pulp. 相似文献
63.
Torbern Tagesson Meelis Mölder Mikhail Mastepanov Charlotte Sigsgaard Mikkel P. Tamstorf Magnus Lund Julie M. Falk Anders Lindroth Torben R. Christensen Lena Ström 《Global Change Biology》2012,18(6):1928-1940
The land‐atmosphere exchange of methane (CH4) and carbon dioxide (CO2) in a high‐Arctic wet tundra ecosystem (Rylekærene) in Zackenberg, north‐eastern Greenland, was studied over the full growing season and until early winter in 2008 and from before snow melt until early winter in 2009. The eddy covariance technique was used to estimate CO2 fluxes and a combination of the gradient and eddy covariance methods was used to estimate CH4 fluxes. Small CH4 bursts were observed during spring thawing 2009, but these existed during short periods and would not have any significant effect on the annual budget. Growing season CH4 fluxes were well correlated with soil temperature, gross primary production, and active layer thickness. The CH4 fluxes remained low during the entire autumn, and until early winter. No increase in CH4 fluxes were seen as the soil started to freeze. However, in autumn 2008 there were two CH4 burst events that were highly correlated with atmospheric turbulence. They were likely associated with the release of stored CH4 from soil and vegetation cavities. Over the measurement period, 7.6 and 6.5 g C m?2 was emitted as CH4 in 2008 and in 2009, respectively. Rylekærene acted as a C source during the warmer and wetter measurement period 2008, whereas it was a C sink for the colder and drier period of 2009. Wet tundra ecosystems, such as Rylekærene may thus play a more significant role for the climate in the future, as temperature and precipitation are predicted to increase in the high‐Arctic. 相似文献
64.
Nicolas Rapin Can Kesmir Sune Frankild Morten Nielsen Claus Lundegaard Søren Brunak Ole Lund 《Journal of biological physics》2006,32(3-4):335-353
Over the past decade a number of bioinformatics tools have been developed that use genomic sequences as input to predict to
which parts of a microbe the immune system will react, the so-called epitopes. Many predicted epitopes have later been verified
experimentally, demonstrating the usefulness of such predictions. At the same time, simulation models have been developed
that describe the dynamics of different immune cell populations and their interactions with microbes. These models have been
used to explain experimental findings where timing is of importance, such as the time between administration of a vaccine
and infection with the microbe that the vaccine is intended to protect against. In this paper, we outline a framework for
integration of these two approaches. As an example, we develop a model in which HIV dynamics are correlated with genomics
data. For the first time, the fitness of wild type and mutated virus are assessed by means of a sequence-dependent scoring
matrix, derived from a BLOSUM matrix, that links protein sequences to growth rates of the virus in the mathematical model.
A combined bioinformatics and systems biology approach can lead to a better understanding of immune system-related diseases
where both timing and genomic information are of importance. 相似文献
65.
The molecular chaperone GroEL is a protein complex consisting of two rings each of seven identical subunits. It is thought to act by providing a cavity in which a protein substrate can fold into a form that has no propensity to aggregate. Substrate proteins are sequestered in the cavity while they fold, and prevented from diffusion out of the cavity by the action of the GroES complex, that caps the open end of the cavity. A key step in the mechanism of action of GroEL is the transmission of a conformational change between the two rings, induced by the binding of nucleotides to the GroEL ring opposite to the one containing the polypeptide substrate. This conformational change then leads to the discharge of GroES from GroEL, enabling polypeptide release. Single ring forms of GroEL are thus predicted to be unable to chaperone the folding of GroES-dependent substrates efficiently, since they are unable to discharge the bound GroES and unable to release folded protein. We describe here a detailed functional analysis of a chimeric GroEL protein, which we show to exist in solution in equilibrium between single and double ring forms. We demonstrate that whereas the double ring form of the GroEL chimera functions effectively in refolding of a GroES-dependent substrate, the single ring form does not. The single ring form of the chimera, however, is able to chaperone the folding of a substrate that does not require GroES for its efficient folding. We further demonstrate that the double ring structure of GroEL is likely to be required for its activity in vivo. 相似文献
66.
Background
Macrophages represent the front lines of our immune system; they recognize and engulf pathogens or foreign particles thus initiating the immune response. Imaging macrophages presents unique challenges, as most optical techniques require labeling or staining of the cellular compartments in order to resolve organelles, and such stains or labels have the potential to perturb the cell, particularly in cases where incomplete information exists regarding the precise cellular reaction under observation. Label-free imaging techniques such as Raman microscopy are thus valuable tools for studying the transformations that occur in immune cells upon activation, both on the molecular and organelle levels. Due to extremely low signal levels, however, Raman microscopy requires sophisticated image processing techniques for noise reduction and signal extraction. To date, efficient, automated algorithms for resolving sub-cellular features in noisy, multi-dimensional image sets have not been explored extensively.Results
We show that hybrid z-score normalization and standard regression (Z-LSR) can highlight the spectral differences within the cell and provide image contrast dependent on spectral content. In contrast to typical Raman imaging processing methods using multivariate analysis, such as single value decomposition (SVD), our implementation of the Z-LSR method can operate nearly in real-time. In spite of its computational simplicity, Z-LSR can automatically remove background and bias in the signal, improve the resolution of spatially distributed spectral differences and enable sub-cellular features to be resolved in Raman microscopy images of mouse macrophage cells. Significantly, the Z-LSR processed images automatically exhibited subcellular architectures whereas SVD, in general, requires human assistance in selecting the components of interest.Conclusions
The computational efficiency of Z-LSR enables automated resolution of sub-cellular features in large Raman microscopy data sets without compromise in image quality or information loss in associated spectra. These results motivate further use of label free microscopy techniques in real-time imaging of live immune cells. 相似文献67.
Lymphotoxin-alpha-deficient mice make delayed,but effective,T and B cell responses to influenza 总被引:6,自引:0,他引:6
Lund FE Partida-Sánchez S Lee BO Kusser KL Hartson L Hogan RJ Woodland DL Randall TD 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(9):5236-5243
Lymphotoxin-alpha(-/-) (LTalpha(-/-)) mice are thought to be unable to generate effective T and B cell responses. This is attributed to the lack of lymph nodes and the disrupted splenic architecture of these mice. However, despite these defects we found that LTalpha(-/-) mice could survive infection with a virulent influenza A virus. LTalpha(-/-) mice and normal wild-type mice infected with influenza A generated similar numbers of influenza-specific CD8 T cells that were able to produce IFN-gamma and kill target cells presenting influenza peptides. Furthermore influenza-infected LTalpha(-/-) mice produced high titers of influenza-specific IgM, IgG, and IgA. However, both CD8 and B cell immune responses were delayed in LTalpha(-/-) mice by 2-3 days. The delayed cellular and humoral immune response was sufficient to mediate viral clearance in LTalpha(-/-) mice that were infected with relatively low doses of influenza virus. However, when LTalpha(-/-) mice were infected with larger doses of influenza, they succumbed to infection before the immune response was initiated. These results demonstrate that neither LTalpha nor constitutively organized lymphoid tissues, such as lymph nodes and spleen, are absolutely required for the generation of effective immunity against the respiratory virus influenza A. However, the presence of LTalpha and/or lymph nodes does accelerate the initiation of immune responses, which leads to protection from larger doses of virus. 相似文献
68.
Nikola Vukovic Brian Hansen Torben Ellegaard Lund Sune Jespersen Yury Shtyrov 《PLoS biology》2021,19(6)
Despite the clear importance of language in our life, our vital ability to quickly and effectively learn new words and meanings is neurobiologically poorly understood. Conventional knowledge maintains that language learning—especially in adulthood—is slow and laborious. Furthermore, its structural basis remains unclear. Even though behavioural manifestations of learning are evident near instantly, previous neuroimaging work across a range of semantic categories has largely studied neural changes associated with months or years of practice. Here, we address rapid neuroanatomical plasticity accompanying new lexicon acquisition, specifically focussing on the learning of action-related language, which has been linked to the brain’s motor systems. Our results show that it is possible to measure and to externally modulate (using transcranial magnetic stimulation (TMS) of motor cortex) cortical microanatomic reorganisation after mere minutes of new word learning. Learning-induced microstructural changes, as measured by diffusion kurtosis imaging (DKI) and machine learning-based analysis, were evident in prefrontal, temporal, and parietal neocortical sites, likely reflecting integrative lexico-semantic processing and formation of new memory circuits immediately during the learning tasks. These results suggest a structural basis for the rapid neocortical word encoding mechanism and reveal the causally interactive relationship of modal and associative brain regions in supporting learning and word acquisition.This combined neuroimaging and brain stimulation study reveals rapid and distributed microstructural plasticity after a single immersive language learning session, demonstrating the causal relevance of the motor cortex in encoding the meaning of novel action words. 相似文献
69.
N-Acetylglutamate is present in foetal rat liver at 17 days' gestation. The tissue content (approx. 50 nmol/g wet wt.) remains constant during later foetal life. The appearance of N-acetylglutamate does not parallel the developmental pattern of the urea cycle. 相似文献
70.
Nanna Brink Scholz Lars Bolund Mette Nyegaard Louise Faaborg Mette Warming J?rgensen Helle Lund Isa Niemann Lone Sunde 《PloS one》2015,10(11)
Hydatidiform moles (HMs) are abnormal human pregnancies with vesicular chorionic villi, imposing two clinical challenges; miscarriage and a risk of gestational trophoblastic neoplasia (GTN). The parental type of most HMs are either diandric diploid (PP) or diandric triploid (PPM). We consecutively collected 154 triploid or near-triploid samples from conceptuses with vesicular chorionic villi. We used analysis of DNA markers and/or methylation sensitive-MLPA and collected data from registries and patients records. We performed whole genome SNP analysis of one case of twinning (PP+PM).In all 154 triploids or near-triploids we found two different paternal contributions to the genome (P1P2M). The ratios between the sex chromosomal constitutions XXX, XXY, and XYY were 5.7: 6.9: 1.0. No cases of GTN were observed. Our results corroborate that all triploid human conceptuses with vesicular chorionic villi have the parental type P1P2M. The sex chromosomal ratios suggest approximately equal frequencies of meiosis I and meiosis II errors with selection against the XYY conceptuses or a combination of dispermy, non-disjunction in meiosis I and meiosis II and selection against XYY conceptuses. Although single cases of GTN after a triploid HM have been reported, the results of this study combined with data from previous prospective studies estimate the risk of GTN after a triploid mole to 0% (95% CI: 0–1,4%). 相似文献